I've got a question! If you want to replace the adverbial clause of the following sentence by a participle construction, what would you say?

Since they were disappointed with the outcome, the workers went on strike.

-> Being disappointed with the outcome the workers went on strike. -> OR: Disappointed with the outcome the workers went on strike.

Is there a difference in meaning? Our textbook suggests that you use the first construction (being disappointed) because the adverbial clause of reason has got an active meaning. Is it possible to see it as follows: They had been disappointed by the outcome, therefore the adverbial clause also has passive meaning, which makes it possible to use a past participle construction, too?